AEROBIC respiration: The LINK REACTION and the KREBS CYCLE for AQA A-level Biology.

Summary

This video provides a detailed explanation of the link reaction and the Krebs cycle, two key stages in aerobic respiration. It breaks down the processes that occur in the mitochondrial matrix, including how pyruvate from glycolysis is converted into acetyl-CoA, the production of NADH, and the release of carbon dioxide. The video also covers the Krebs cycle, where acetyl-CoA reacts with a four-carbon molecule to form a six-carbon molecule, producing ATP, NADH, FADH2, and carbon dioxide. The cycle occurs twice for each glucose molecule, highlighting its role in energy production and cellular respiration.

Takeaways

• 😀 Glycolysis is the first stage of aerobic respiration and occurs in the cytoplasm, while the link reaction and Krebs cycle occur in the mitochondrial matrix.
• 😀 The link reaction converts pyruvate into acetyl CoA, producing NADH and releasing carbon dioxide in the process.
• 😀 NADH is produced in both the link reaction and Krebs cycle, but it is only used in the final stage of aerobic respiration, oxidative phosphorylation.
• 😀 One glucose molecule generates two pyruvates, so the link reaction occurs twice for each glucose molecule.
• 😀 In the Krebs cycle, acetyl CoA combines with a four-carbon molecule to form a six-carbon molecule, releasing CoA for reuse.
• 😀 The Krebs cycle involves a series of redox reactions that break down the six-carbon molecule, releasing two molecules of carbon dioxide.
• 😀 ATP is produced during the Krebs cycle, and the cycle generates reduced NAD and FAD (NADH and FADH2) as coenzymes.
• 😀 For each round of the Krebs cycle, the products are 3 NADH, 1 FADH2, 1 ATP, and 2 carbon dioxide molecules.
• 😀 Since each glucose molecule creates two pyruvates, the Krebs cycle happens twice, doubling the number of products.
• 😀 The link reaction and Krebs cycle both take place in the mitochondrial matrix, which is crucial for energy production in aerobic respiration.

Q & A

What is the main focus of this video?

The main focus of the video is explaining the link reaction and the Krebs cycle, which are part of aerobic respiration, and occur in the mitochondrial matrix.

Where does glycolysis occur, and how does it relate to the link reaction?

Glycolysis occurs in the cytoplasm, and its products, pyruvate and reduced NADH, must be transported into the mitochondrial matrix for the link reaction.

What are the main products of glycolysis that are used in the link reaction?

The main products of glycolysis used in the link reaction are pyruvate and reduced NADH (NADH).

What happens to pyruvate in the link reaction?

Pyruvate is oxidized into acetate, which involves the loss of hydrogen. This hydrogen is picked up by NAD to form NADH, and one carbon atom is released as carbon dioxide.

Why is carbon dioxide produced during the link reaction?

Carbon dioxide is produced during the link reaction because pyruvate, a three-carbon molecule, is converted into acetate, a two-carbon molecule, releasing one carbon atom as CO2.

What is the role of coenzyme A in the link reaction?

Coenzyme A combines with acetate to form acetyl coenzyme A (acetyl-CoA), which is essential for the next step in the Krebs cycle.

How many times does the link reaction occur for one glucose molecule?

The link reaction occurs twice for one glucose molecule because one glucose molecule produces two pyruvates.

What are the key products of the Krebs cycle for one round?

For one round of the Krebs cycle, the products are three reduced NADH, one reduced FADH2, one ATP, and two molecules of carbon dioxide.

How many times does the Krebs cycle occur for one glucose molecule?

The Krebs cycle occurs twice for one glucose molecule because two acetyl-CoA molecules are produced from one glucose molecule.

What is the role of NADH and FADH2 in the Krebs cycle?

NADH and FADH2 are reduced coenzymes that carry electrons and protons. They are produced through redox reactions during the Krebs cycle and will be used in the final stage of aerobic respiration, oxidative phosphorylation.